RegdatXP reads non active WinNT/2K/XP/2K3 registry files like Ntuser.dat and usrClass.dat and compares them to the current Registry. It has also (binary) Search and Replace functions for the Registry. The full version can directly repair corrupt registry files in some cases. The Registry as displayed by Regedit or Regedt32 is composed of the following root keys: HKLM HKEY_LOCAL_MACHINE This contains all the information in the current SOFTWARE, SYSTEM, SAM, and SECURITY files of the System32Config directory. HKU HKEY_USERS This key contains the .Default and other user keys and a repetition of the HKEY_CURRENT_USER key. HKCU HKEY_CURRENT_USER This contains all the information stored in the Ntuser.dat and usrClass.dat of the current user.